noun
- An insect of the order Ephemeroptera, commonly known as a mayfly, characterized by a short adult lifespan and aquatic nymphal stage.
Usage: technical; zoology
Examples
- The ephemerid emerged from the stream and lived for only a few hours as an adult.
- Fishermen study ephemerids to understand what trout feed on in rivers.
- The nymph stage of an ephemerid can last for one to three years underwater.
- Ephemerids are important indicators of water quality in freshwater ecosystems.